BlackBerry smartphones are especially popular among urban teenagers, accounting for 37 per cent of the market according to Ofcom. They are cheap compared to rival smartphones and the built-in BBM service offers a very low cost alternative to text messaging.

It presents a particular challenge to police attempting to track disturbances, because it acts as a hybrid of traditional text messaging and a social network such as Twitter: communication is quasi-private, but it is possible to “broadcast” messages to many users.

On Monday, RIM pledged to help investigators “in any way we can”, but David Lammy, the Labour MP for Tottenham, called for BBM to be shut down at the height of the disturbances.

He was backed last night by the Tory MP Louise Mensch, who suggested on Twitter that communication networks should be shut down during riots.

“If riot info and fear is spreading by Facebook and Twitter, shut them off for an hour or two, then restore. World won't implode,” she said.

Police already have powers to access stored data and monitor social networks in real time under the Police and Criminal Evidence Act, and the Regulation of Investigatory Powers Act. Nevertheless, in his speech to Parliament yesterday, David Cameron said new powers were under consideration.

“We are working with the police, the intelligence services and industry to look at whether it would be right to stop people communicating via these websites and services when we know they are plotting violence, disorder and criminality,” he said.